Experimental study of the critical incidence phenomena in low speed compressor stators with both conventional and 3D blading designs

Abstract Three-dimensional (3D) corner separation, which can arise significant flow blockage and loss production, is an inherent and detrimental flow feature inside the stator of axial compressors, hence, numerous active and passive methods have been investigated to prevent the corner separation turning into corner stall in recent years. This paper investigates experimentally the 3D separating flows and the Critical Incidence Phenomenon inside the stator passage of a serious of low-speed large-scale axial compressors with or without 3D blading designs, and it is expected that some rules for design of highly loaded stator could be found. Firstly, the experimentally observed Critical Incidence Phenomenon in the previous study was reviewed, and this phenomenon was validated in the other compressors with different design parameters. Then, the effects of blade loading, blade airfoils, and 3D blading designs on the critical incidence were discussed. And the results revealed that blade loading and 3D blading designs seem to have no impact on the critical incidence, while blade airfoils should be considered as an impact factor on it. Besides, though 3D blading designs could not increase the critical incidence, it can reduce the actual inlet incidence instead, hence, after the stator is redesigned using the 3D stacking, the corner stall is delayed. Finally, based on the above-mentioned analysis, a critical-incidence-based metric named Incidence Reserve was proposed to guide the design of the highly loaded stator. It is expected that at the initial stage of a stator the distribution of the Incidence Reserve along the span is as consistent as possible, so that the detrimental hub corner stall will be eliminated or deferred.